Create new inset algorithm for spot shadows

BUG=skia:

Change-Id: If7c67c2a5b9beea28f86d13362a5156b46394d0e
Reviewed-on: https://skia-review.googlesource.com/9875
Commit-Queue: Ravi Mistry <rmistry@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>

1 files changed, 132 insertions, 0 deletions

diff --git a/tests/InsetConvexPolyTest.cpp b/tests/InsetConvexPolyTest.cpp
new file mode 100644
index 0000000000..e13a25a70f
--- /dev/null
+++ b/tests/InsetConvexPolyTest.cpp
@@ -0,0 +1,132 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#include "Test.h"
+#include "SkInsetConvexPolygon.h"
+
+static bool is_convex(const SkTDArray<SkPoint>& poly) {
+    if (poly.count() < 3) {
+        return false;
+    }
+
+    SkVector v0 = poly[0] - poly[poly.count() - 1];
+    SkVector v1 = poly[1] - poly[poly.count() - 1];
+    SkScalar winding = v0.cross(v1);
+
+    for (int i = 0; i < poly.count()-1; ++i) {
+        int j = i + 1;
+        int k = (i + 2) % poly.count();
+
+        SkVector v0 = poly[j] - poly[i];
+        SkVector v1 = poly[k] - poly[i];
+        SkScalar perpDot = v0.cross(v1);
+        int side = winding*perpDot;
+        if (side < 0) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+DEF_TEST(InsetConvexPoly, reporter) {
+    SkTDArray<SkPoint> rrectPoly;
+
+    // round rect
+    *rrectPoly.push() = SkPoint::Make(-100, 55);
+    *rrectPoly.push() = SkPoint::Make(100, 55);
+    *rrectPoly.push() = SkPoint::Make(100 + 2.5f, 50 + 4.330127f);
+    *rrectPoly.push() = SkPoint::Make(100 + 3.535534f, 50 + 3.535534f);
+    *rrectPoly.push() = SkPoint::Make(100 + 4.330127f, 50 + 2.5f);
+    *rrectPoly.push() = SkPoint::Make(105, 50);
+    *rrectPoly.push() = SkPoint::Make(105, -50);
+    *rrectPoly.push() = SkPoint::Make(100 + 4.330127f, -50 - 2.5f);
+    *rrectPoly.push() = SkPoint::Make(100 + 3.535534f, -50 - 3.535534f);
+    *rrectPoly.push() = SkPoint::Make(100 + 2.5f, -50 - 4.330127f);
+    *rrectPoly.push() = SkPoint::Make(100, -55);
+    *rrectPoly.push() = SkPoint::Make(-100, -55);
+    *rrectPoly.push() = SkPoint::Make(-100 - 2.5f, -50 - 4.330127f);
+    *rrectPoly.push() = SkPoint::Make(-100 - 3.535534f, -50 - 3.535534f);
+    *rrectPoly.push() = SkPoint::Make(-100 - 4.330127f, -50 - 2.5f);
+    *rrectPoly.push() = SkPoint::Make(-105, -50);
+    *rrectPoly.push() = SkPoint::Make(-105, 50);
+    *rrectPoly.push() = SkPoint::Make(-100 - 4.330127f, 50 + 2.5f);
+    *rrectPoly.push() = SkPoint::Make(-100 - 3.535534f, 50 + 3.535534f);
+    *rrectPoly.push() = SkPoint::Make(-100 - 2.5f, 50 + 4.330127f);
+    REPORTER_ASSERT(reporter, is_convex(rrectPoly));
+
+    // inset a little
+    SkTDArray<SkPoint> insetPoly;
+    bool result = SkInsetConvexPolygon(&rrectPoly[0], rrectPoly.count(), 3, &insetPoly);
+    REPORTER_ASSERT(reporter, result);
+    REPORTER_ASSERT(reporter, is_convex(insetPoly));
+
+    // inset to rect
+    result = SkInsetConvexPolygon(&rrectPoly[0], rrectPoly.count(), 10, &insetPoly);
+    REPORTER_ASSERT(reporter, result);
+    REPORTER_ASSERT(reporter, is_convex(insetPoly));
+    REPORTER_ASSERT(reporter, insetPoly.count() == 4);
+    if (insetPoly.count() == 4) {
+        REPORTER_ASSERT(reporter, insetPoly[0].equals(-95, 45));
+        REPORTER_ASSERT(reporter, insetPoly[1].equals(95, 45));
+        REPORTER_ASSERT(reporter, insetPoly[2].equals(95, -45));
+        REPORTER_ASSERT(reporter, insetPoly[3].equals(-95, -45));
+    }
+
+    // just to full inset
+    // for shadows having a flat poly here is fine
+    // may want to revisit for strokes
+    result = SkInsetConvexPolygon(&rrectPoly[0], rrectPoly.count(), 55, &insetPoly);
+    REPORTER_ASSERT(reporter, result);
+    REPORTER_ASSERT(reporter, is_convex(insetPoly));
+    REPORTER_ASSERT(reporter, insetPoly.count() == 4);
+    if (insetPoly.count() == 4) {
+        REPORTER_ASSERT(reporter, insetPoly[0].equals(-50, 0));
+        REPORTER_ASSERT(reporter, insetPoly[1].equals(50, 0));
+        REPORTER_ASSERT(reporter, insetPoly[2].equals(50, 0));
+        REPORTER_ASSERT(reporter, insetPoly[3].equals(-50, 0));
+    }
+
+    // past full inset
+    result = SkInsetConvexPolygon(&rrectPoly[0], rrectPoly.count(), 75, &insetPoly);
+    REPORTER_ASSERT(reporter, !result);
+
+    // troublesome case
+    SkTDArray<SkPoint> clippedRRectPoly;
+    *clippedRRectPoly.push() = SkPoint::Make(335.928101f, 428.219055f);
+    *clippedRRectPoly.push() = SkPoint::Make(330.414459f, 423.034912f);
+    *clippedRRectPoly.push() = SkPoint::Make(325.749084f, 417.395508f);
+    *clippedRRectPoly.push() = SkPoint::Make(321.931946f, 411.300842f);
+    *clippedRRectPoly.push() = SkPoint::Make(318.963074f, 404.750977f);
+    *clippedRRectPoly.push() = SkPoint::Make(316.842468f, 397.745850f);
+    *clippedRRectPoly.push() = SkPoint::Make(315.570068f, 390.285522f);
+    *clippedRRectPoly.push() = SkPoint::Make(315.145966f, 382.369965f);
+    *clippedRRectPoly.push() = SkPoint::Make(315.570068f, 374.454346f);
+    *clippedRRectPoly.push() = SkPoint::Make(316.842468f, 366.994019f);
+    *clippedRRectPoly.push() = SkPoint::Make(318.963074f, 359.988892f);
+    *clippedRRectPoly.push() = SkPoint::Make(321.931946f, 353.439056f);
+    *clippedRRectPoly.push() = SkPoint::Make(325.749084f, 347.344421f);
+    *clippedRRectPoly.push() = SkPoint::Make(330.414459f, 341.705017f);
+    *clippedRRectPoly.push() = SkPoint::Make(335.928101f, 336.520813f);
+    *clippedRRectPoly.push() = SkPoint::Make(342.289948f, 331.791901f);
+    *clippedRRectPoly.push() = SkPoint::Make(377.312134f, 331.791901f);
+    *clippedRRectPoly.push() = SkPoint::Make(381.195313f, 332.532593f);
+    *clippedRRectPoly.push() = SkPoint::Make(384.464935f, 334.754700f);
+    *clippedRRectPoly.push() = SkPoint::Make(386.687042f, 338.024292f);
+    *clippedRRectPoly.push() = SkPoint::Make(387.427765f, 341.907532f);
+    *clippedRRectPoly.push() = SkPoint::Make(387.427765f, 422.832367f);
+    *clippedRRectPoly.push() = SkPoint::Make(386.687042f, 426.715576f);
+    *clippedRRectPoly.push() = SkPoint::Make(384.464935f, 429.985168f);
+    *clippedRRectPoly.push() = SkPoint::Make(381.195313f, 432.207275f);
+    *clippedRRectPoly.push() = SkPoint::Make(377.312134f, 432.947998f);
+    *clippedRRectPoly.push() = SkPoint::Make(342.289948f, 432.947998f);
+    REPORTER_ASSERT(reporter, is_convex(clippedRRectPoly));
+
+    result = SkInsetConvexPolygon(&clippedRRectPoly[0], clippedRRectPoly.count(), 32.3699417f,
+                                  &insetPoly);
+    REPORTER_ASSERT(reporter, result);
+    REPORTER_ASSERT(reporter, is_convex(insetPoly));
+}